Click Date Range > Custom > select dates of A/B test
Click Group By Time > Entire Range
Click Customize and select the following fields to include in the report:
Click Export
Download the report
Many sign up units may appear, but we are only interested in the ones associated with the A/B test. Filter the sheet to include only sign up units from the A/B test
Copy and paste results into the Attentive Export tab of the Google Sheet Report you created